A semiconductor device typically includes a network of circuits that are formed over a substrate. The device may include several layers of circuit wiring, with various interconnects being used to connect these layers to each other and any underlying transistors. The fabrication of semiconductor devices may utilize a series of lithographic and etching steps to define the positions and dimensions of various features.
As the trend towards miniaturization continues, semiconductors are being produced with smaller critical dimensions (CDs) and tighter pitches. As the critical dimension miniaturizes below the 22 nm node, new challenges are pushing conventional lithography to its limits.
Block copolymer (BCP) patterning has attracted attention as a possible solution to the problem of creating patterns with smaller dimensions. Under the right conditions, the blocks of such copolymers phase separate into microdomains (also known as “microphase-separated domains” or “domains”) to reduce the total free energy, and in the process, nanoscale features of dissimilar chemical compositions are formed. The ability of block copolymers to form such features recommends their use in nanopatterning, and to the extent that features with smaller CDs can be formed, this should enable the construction of features which would otherwise be difficult to print using conventional lithography. However, without any guidance from the substrate, the microdomains in a self-assembled block copolymer thin film are typically not spatially registered or aligned.
To address the problem of spatial registration and alignment, directed self-assembly (DSA) has been used. This is a method that combines aspects of self-assembly with a lithographically defined substrate to control the spatial arrangement of certain self-assembled BCP domains. It is therefore desirable to have improvements in directed self-assembly of block copolymers.